Electric piezoid amplifiers



H. E. HOLLMANN 2,810,023

ELECTRIC PIE-ZOID AMPLIFIERS Oct. 15, 1957 Filed Nov. 15, 1949 SE/GNETTE- EL E 6 TRIO CRYS TAL Fig.2

ELECTRIC CRYSTAL INVENTOR. Hans E. Hal/mam 2,810,023 I j ELECTRIC PIEZOID' AMPLIFIERS Hans E. Hollmann, Camarillo, Calif., assignor to the United States or America as represented by the Secretary of the Navy Application November 15, 1949, Serial No. 127,472 3 Claims. (Cl. 179171) (Granted under Title 35, U. S. Code (1952), see. 266) This invention relates toan electric piezoid amplifier, and is predicated on the varying dielectric constant with.

varying field strength of certain dipole substances such as Rochelle salt and other crystals displaying Seignette electricity.

It is an object of this invention to provide a simplified amplifier capable of translating small alternating or fluctuating signals into larger, corresponding signals across an output impedance.

It is another object of this invention to provide such an amplifier employing only durable solid materials, thereby obviating the difiiculties associated with use of an evacuated envelope now commonly employed.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following description.

The instant amplifier consists of an insulating medium or crystal such as a crystal of Rochelle salt, having a dielectric constant which varies with the electric field strength within the medium. Adjacent or embracing the medium is a pair of plate electrodes to which are connected a source of. direct or supply voltage and an output or load impedance. A second pair of electrodes is also disposed adjacent or embracing the medium, and to these electrodes there is connected in series a source of fluctuating voltage constituting an input voltage. A source of direct voltage bias is also preferably connected to the second circuit including the second pair of electrodes.

In a preferred form of the instant invention, the insulating medium described above consists of a crystal. It is further preferred to place the two pairs of electrodes at right angles to each other, so that the crystal is spanned or embraced on four sides. It is further preferred to so cut the crystal that the electric field sensitive X axis of the crystal is oriented midway-that is to say, at an angle of 45 --between the two pairs of electrodes.

Referring to the drawing,

Fig. 1 represents a preferred modification of the instant invention; and

Fig. 2 shows an alternate construction.

In Fig. 1, 11 designates a capacitor consisting of a generally cubicle block of insulating material 12, having a dielectric constant which varies with the electric field strength within the medium. The dielectric medium 12 is preferably a crystal such as a crystal of Rochelle salt, or other crystal, displaying Seignette electricity.

Capacitor 11 further includes a pair of electrodes 13 and 14, disposed adjacent the medium 12, and embracing it on its horizontal faces; and a second pair of electrodes 16 and 17, disposed perpendicular to the electrodes 13 and 14 so as to embrace the medium 12 on its vertical faces. If a crystal is chosen for the medium 12, it is preferred to cut it so that the X axis is angularly disposed midway between the electrodes 13--14 and 1617, that is, at an angle of 45 with respect to each pair of electrodes, as shown by the axis line 18 in Fig. 1.

* United States 2,310,023 Patented Oct. 15, 1957 To the capacitor 11 isconnected a source of direct or supply voltage as illustrated by the battery 19, and

an output or load impedance 21,. these elements preferably being connected in series with the electrodes 13.

and 14. Also to the capacitor 11, in this case to the electrodes 16 and 17, is connected a source of fluctuating (in this case, alternating) signal voltage 22. A source of direct biasing voltage 23 is preferablyconnected in series with the source 22 and the electrodes 1617.

In operation, thefluctuating potential from the source 22 creates a fluctuating electric field in the medium 12, which is directly proportional to the signal from source 22. The varying field strength in the medium 12 causes a corresponding variation in the capacity extent between the electrodes 13 and 14, so that there is a current flow set up through the load impedance 21 from the battery signal expected from the source 22.

In Fig. 2, another embodiment of the instant invention is shown, wherein the two pairs of electrodes are parallel to each other instead of being perpendicular as in Fig. 1. As shown in Fig. 2, a single large electrode 24 occupies the bottom face of the medium 120, while the top face is covered by two electrodes, 13a and 17a.

Both of the electrodes 13a and 17a make use of the common electrode 24 to complete a capacitor employing medium 12a as its dielectric medium. The output electrode 13a is conencted to an output impedance 21a and a supply voltage 19a, while the input electrode 17a is connected to a bias battery 23a and an input source of alternating potential 22a.

The operation of the circuit of Fig. 2 is substantially the same as that described in Fig. 1, except that the controlling or fluctuating electric field is produced in a direction parallel to that of the principal capacitor constituted by the electrodes 13a and 24.

The circuit of Fig. 1 is preferred because the perpendicular disposition of the two pairs of electrodes tends to avoid any natural capacity coupling between the input and output circuits, which might counteract the desired trans-capacity of amplification.

The output voltage, and likewise the gain, of the instant amplifier may be increased as in the case of a vacuum tube amplifier by increasing the value of the output impedance 21, but, as in the case of a vacuum tube, the supply voltage 19 must also be increased in order to assure a suitable operating point on the nonlinear characteristic of the dielectric medium 12.

As in any amplifier the gain may be increased considerably by the aid of positive feedback connected in any suitable and well known fashion.

By substituting a parallel resonant circuit for the output impedance 21, and including necessary feedback, the instant amplifier may be transformed into an oscillator, just as in the case of any known type of amplifier.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An amplifier which comprises a Seignette-electric crystal having a first pair of parallel faces and a second I pair of parallel faces disposed perpendicularly to said first aces, a first pair of spaced electrodes disposed adjacent said first pair of faces, a second pair of spaced electrodes disposed adjacent said second pair offaces, a source of direct voltage nected to said first electrodes, a source of fluctuating voltage connected to said second electrodes, the electric field sensitive X axis of said crystal being positioned along a diagonal line between opposite edges of said crystal formed by the intersection of said first and second faces.

2. An amplifier which comprisesa Seignette-electric crystal having a first pair of parallel faces and a second pair of parallel faces disposed perpendicularly to said first faces, a first pair of spaced electrodes disposed adjacent said first pair of faces, a second pair of spaced electrodes disposed adjacent said second pair of faces and substantially at right angles to said first electrodes, a source of direct voltage and a load impedance conand a load impedance con -crystal has a substantially 1,769,360 Thomas July 1, 1930 1,778,796 Craig Oct. 21, 1930 2,071,564 Nicolson Feb. 23, 1937 2,306,555 Mueller Dec. 29, 1942 2,464,807 Hansen Mar. 22, 1949 2,470,893 Hepp May 24, 1949 4 'nec't ed'in series with said first electrodes, a source of fluctuating voltage and a source of direct voltage bias connected in series with said second electrodes, the electric field sensitive X axis of said crystal being positioned along a diagonal line between opposite edges of said crystal formed by the intersection of said first and second faces.

3. An amplifier as defined in claim 2 wherein said ration and said X axis forms a degree angle with said pairs of electrodes.

References Cited in the file of this patent UNITED STATES PATENTS square cross-sectional configu- 

